Propulsion systems of the future will involve missions requiring bold increases in performance over present systems. New and innovative concepts are therefore required to meet these future needs. The present invention relates to a completely new and unique apparatus for achieving missile total thrust control that offers the combined capabilities of very high side force control ("thrust vector control" or "TVC"), axial thrust modulation control ("thrust magnitude control" or "TMC") and roll control ("RC"), all within a compact nozzle system.
One of the principal disadvantages to the use of present day solid propellant engines in complex trajectory applications is their inability to effectively manage or vary the main (axial) nozzle thrust (i.e., TMC). This single attribute, in spite of the superior storability, simplicity and lower cost of solids, often leads to inefficiencies and system inflexibilities that can drastically limit missile system performance and/or necessitate the use of boost/sustain and other complex and expensive propellant grain designs to achieve thrust shaping.
Similarly, the inherent and strict mechanical limitations and the complexities of many present day TVC systems impose restrictions on the TVC system performance that can be obtained with these concepts. Side force magnitudes and reversal rates therefore limit missile system target acquisition and kill performance.
The present invention seeks to enhance TMC while supplying the added capability of very high side forces and very high side force reversal rates. Since motors equipped with the present invention can be designed to meet the unique axial and side force requirements of a specific mission, the performance of the resulting propulsion systems is not driven by specific subsystem limitations. This enables each missile propulsion system to be optimized to its own individual mission parameters.
High performance propulsion systems of the future must, therefore, have two major performance capabilities. These are energy management and maneuverability. These two primary capabilities when coupled with reliable and cost effective missile concept design approaches will result in missile systems of superior caliber. The present invention offers the capability of achieving both of these goals (plus roll control) in a single compact nozzle apparatus.
System performance studies involving the missions of future high performance missile systems show three irrefutable results. First, the vulnerability of the launching platform (aircraft, ship, tank, etc.) is measurably reduced with greater launch standoff distances. Second, the missile kill envelope is driven at the inner boundary by missile maneuverability (i.e., side force parameters) and at the outer boundary by missile range. And third, the largest single contributor to increased missile range results from reducing its aerodynamic drag coefficient. Aerodynamic wings and control surfaces necessarily cause increases in the missile drag coefficient.
With the present invention, aerodynamic drag is reduced, since no aerodynamic control surfaces are necessarily required. Also because of the present invention's TMC capability, it is often possible, by throttling down after the missile cruise speed has been achieved, to extend the missile range and the time of powered flight to target intercept and destruction. In so doing, the missile can maintain the minimum necessary control forces in powered flight and then throttle-up just prior to the target engagement to achieve the present invention's capability of extremely high side forces and side force reversal-rates for use during the target intercept phase.
One prior art disclosure for producing control moments in rocket-propelled missile systems is disclosed in U.S. Pat. No. 3,802,190 (Kaufmann), issued Apr. 9, 1974. Kaufman discloses a rocket-propelled missile including a housing for a rocket engine having a plurality of control-nozzle assemblies attached to the outer skin of the missile around its periphery. Each assembly is continuously supplied with thrust gases, and includes a thrust discharge in the same direction as the main nozzle thrust and at least one additional thrust discharge extending outwardly in a tangential direction. No radial nozzles are present in the control nozzle assemblies. Control means are provided for controlling gas flow to the nozzles in each control nozzle assembly. In a further disclosed embodiment, each assembly is also provided with an axial nozzle having a thrust direction opposite to the main axial nozzle thrust to produce additional control moments. Gases are continuously directed to the control nozzle assemblies. Consequently, axial thrust is not modulated in Kaufman through the diversion of gases from the main nozzle to the control nozzle assemblies.
The present invention offers numerous advantages over the prior art disclosed in Kaufman. First, there are no control nozzles distributed over the missile surface, so there is no increase in the drag coefficient of the missile. Second, the control nozzles either increase the total net axial thrust of the missile, or do not affect the total axial thrust. Third, roll torque and pitch or yaw moments can be simultaneously produced. Fourth, the missile control moments are not limited by the physical radius of the missile. And finally, the present invention does not require a continuous flow of propellant gases through each nozzle control assembly for the entire fuel burning duration, so that heat buildup and material erosion/corrosion problems on the seals, nozzles and mechanical components of the system are minimized.
Another missile control system is disclosed in U.S. Pat. No. 3,350,886 (Feraud et al.), issued Nov. 7, 1967. The disclosed system provides for the stabilization and guidance of rocket-propelled vehicles operating along powered or unpowered ballistic phases of flight.
This system is intended primarily for liquid fuel sounding rockets. In powered flight, pitch and yaw control are effected through liquid or gas-injection in the main propulsion nozzle supersonic flowstream to deflect the main jet or thrust vector to achieve side forces. Pitch and yaw control in ballistic flight and roll control in both powered and ballistic flight are achieved by selectively supplying compressed gas to a system of nozzles. The Feraud et al. disclosure does not allow unlimited freedom as to which nozzles can be opened and closed at the same time. For example, certain sets of nozzles can only be actuated in pairs, whereas other sets of nozzles allow only one or the other of a pair to be actuated at a single time. Also, Feraud et al. contains no suggestion of axial thrust modulation by flow diversion.
Accordingly, there is a need in the art for a missile control system that is capable of controlling pitch, yaw and roll forces and moments, as well as main nozzle axial thrust, without greatly increasing the weight, complexity or drag of the missile.